Possible Clues:

• Crab or shrimp, e.g.
• Crab takes a month on a case …
• A shrimp, crab or lobster
• Crab or shrimp, e.g
• Lobster, say, upset brill on hull under dam
• Crab for one to behead? Dangerous thing to take!
• Crab, say, walked to the left, then round back of pond
• Retired cook regulated time for lobster, say
• Creature with several legs as before walked up
• Crab maybe walked about, almost curious